I completely forgot Smash TV and the Star Wars games, which I rented multiple times. The Star Wars games were fun action platformers and Smash TV was just awesome.
I now remember that my SNES was so old that Mario RPG would freeze on me, which is why I never bought it.
My list of uber-awesome-under-the-rader SNES games
Faceball 2000 - Played this so much, especially the multiplayer. It was a First Person labrynth game with smilies that could shoot each other. Multiplayer was basically Deathmatch in mazes.
Zombies ate my Nieghbors - Awesome game that I wish there was a modern update of. Co-op was aces. Multiple weapons and many weapons worked better versus certain types of enemies. Like using the wheed wacker against the plant growths, or crosses versus vampires. Balloon dummies versus chainsaw maniacs. If Dead Rising had co-op and more than just zombies, it might be like a ZAMN update.
Smash TV - Another great co-op game. Though you can get a good version of it in the MAT.
The Interplay Games
Interplay rocked in the 16bit era before they blew up in the coming gen. Rock & Roll Racing was great, with midi classic rock music, a monster truck show announcer, upgradeable cars and, multiplayer and weapons. The Lost Vikings was a neat little side scrolling puzzle game, that required using all three characters correctly and in the right order. Plus, if you failed you got yelled at by Odin who had some funny lines. They also did Blackthorne, a fine adventure game and Boogerman... a basically disgusting action platformer. I liked the Clayfighter games as well, great characters and Clayfighter 2 had much improved gameplay and balance. A lot of their games were creative and not something I'd see today. Then they went and screwed it up!